r205368 - Partially revert r204517 and fix a different way:

[Eric Christopher]

<snipping to get to the ultimate point>

>
> Slightly misleading - we're not using the body, just the pattern definition.
>
> Honestly I might consider breaking this whole location computation bit
> into a separate function and writing a paragraph-long screed about the
> quirky nature of the AST here & what we're dealing with.
>

Yeah, probably.

-eric